1. Field of the Invention
The present invention relates to an organic light emitting display and method of fabricating the same and, more particularly, to an organic light emitting display and method of fabricating the same in which a subsequent organic layer is deposited by forming an insulating layer pattern having a protruding structure and then forming a pixel electrode in an emission region.
2. Description of the Related Art
An organic light emitting display (OLED) is an emissive display that emits light by electrically exciting a fluorescent organic compound. The OLED is classified into a passive matrix type and an active matrix type according to how the driving N×M pixels are arranged in the matrix. The active matrix OLED consumes less power than the passive matrix OLED making it more suitable for a large-sized display and/or a high resolution display. Also, the OLED is classified into a top emission type, a bottom emission type, and a double-sided emission type based on a direction of light emitted from the organic compound. The top emission OLED emits light in an opposite direction to a substrate having unit pixels and has a high aperture ratio.
The organic compound of the OLED is formed in an emission region of a pixel electrode, which is an anode. A laser induced thermal imaging (LITI) technique or a small molecule deposition technique may be used to form the organic compound.
FIGS. 1A, 1B, and 1C are cross-sectional views illustrating a method of fabricating a conventional OLED. Each of FIGS. 1A, 1B, and 1C illustrates a different stage of fabrication.
Referring to FIGS. 1A, 1B, and 1C, a buffer layer 110 having a predetermined thickness is formed on a substrate 100, and a thin film transistor (TFT) having a polysilicon pattern 122, a gate electrode 132, and source and drain electrodes 150 and 152 are formed thereon. For example, source and drain regions 120, which are ion-implanted, are formed at both sides of the polysilicon pattern 122, and a gate insulating layer 130 is formed over the entire surface including the polysilicon pattern 122.
A passivation layer 160 having a predetermined thickness is formed over the entire surface of the structure and is etched by photolithography and etching processes to form a first via contact hole 162 which exposes the source electrode 150 or the drain electrode 152. The passivation layer 160 may be formed of silicon nitride. Referring to FIG. 1A, the contact hole 162 exposes a portion of the drain electrode 152.
Referring to FIG. 1B, a first insulating layer 170 is formed over the entire surface of the structure for planarization of a pixel region. The first insulating layer 170 may be made of, for example, polyimide, benzocyclobutene-based resin, spin on glass (SOG), or acrylate. The first insulating layer 170 is etched by a photolithography process to form a second contact hole 172 which exposes at least a portion of the first contact hole 162.
Referring to FIG. 1C, a pixel electrode material layer (not shown) is subsequently formed over the entire surface of the structure. The pixel electrode material layer is made of a transparent conductive material, such as, for example, indium tin oxide (ITO). The pixel electrode material layer is etched by a photolithography process to form a pixel electrode 180.
A second insulating layer pattern 190 is subsequently formed over the entire surface of the structure to define a pixel region of the pixel electrode 180. The second insulating layer pattern 190 may be made of polyimide, benzocyclobutene-based resin, phenol resin, or acrylate. An organic layer (not shown) and a cathode (not shown) are subsequently formed using the LITI technique or the small molecule deposition technique, thereby completing the OLED.
As shown in FIG. 1C, when the second insulating layer 190 has a thickness sufficient to fill a contact hole, a step H with a height of at least 5,000 Å is formed between the second insulating layer pattern 190 and the pixel electrode 180 and a portion of the second insulating layer pattern 190 corresponding to an edge of the pixel region forms an angle θ of approximately 50°. Therefore, an edge or portion of an organic layer that is formed by the LITI technique may be separated or removed from a surface of the structure, thereby degrading the characteristics of the OLED.